Time Machine Back-up for my MB

I am now 2 weeks into the world of Apple and loving it. It takes a while to get used to the differences between the PC but I am slowly remembering the keyboard shortcuts... It's great.

One question:

I need to start a time machine back-up and have about 100 gig of files that will go on a 2nd HD (cunningly kept from upgrading my MB manually and put in an Icy Box Enclosure..

So, how long will this back-up take on a USB external HD (100gigs to back-up). Hours?

The reason I ask is that I am encoding loads of DVDs on handbrake and do not know whether to leave the back-up overnight or "The Best of Bowie" DVD encoding overnight ;-) Thanks for any info. Apologies if this may be in the wrong section.

My first backup via Time Machine took place immediately after I upgraded to Leopard. I had less stuff (maybe 50GB) and I use FireWire so I don't remember it taking an incredibly long time...like an hour. It will work in the background as you use your computer but it may slow things down a little.

I guess you should ask yourself...which is more important: Backup or Bowie

[Man I can still remember him and Bing singing Little Drummer Boy on the Bing Crosby Christmas Special. It was amazing.]

when i first backed up my hard drive with time machine it took a long time, but just let it go over night and it will be just fine. it will work without you having to do anything. i had about 80 gigs when i did my first backup btw

How do I just backup my documents & itunes files as my external HD will not fit everything on as a back-up. Is this possible? I notice having to exclude files but I am not sure if excluding applications will also exclude itunes?

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